Transponders are electronic devices incorporated into secure documents such as “smart cards” and “electronic passports” using RFID (radio frequency identification) technology.
The transponder (or inlay, or chip card) itself generally comprises (includes):                a substrate (or inlay substrate) which may comprise a sheet of a synthetic material;        a chip (or chip module, or chip unit) installed on the substrate (or in a recess in the surface of the substrate) and having terminals (or contact surfaces, or pads); and        an antenna wire (or conductor) mounted on the substrate, formed with “turns” as a flat coil and connected (bonded) by its ends (see FIG. 2A) or end portions (see FIG. 2B) to the terminals of the chip. (In some of the drawings presented herein, only one end or end portion of the antenna wire may be shown, for illustrative clarity, particularly in the cross-sectional views.)        
The following dimensions and materials are merely exemplary:                the chip module may be generally rectangular, measuring for example 5 mm×8 mm (width×height), and may have a thickness of approximately 0.5-1 mm                    a first terminal disposed on one end of the chip module may measure for example 4 mm wide×2 mm high—in other words, nearly the entire width of the chip module, and approximately ¼-⅓ its height.            a second terminal disposed on one the other end of the chip module may measure for example 4 mm wide×2 mm high—in other words, nearly the entire width of the chip module, and approximately ¼-⅓ its height.                        The antenna wire may be “heavy” wire (such as 60 μm in diameter) requiring higher bonding loads than those used for “fine” wire (such as 30 μm). Rectangular section copper ribbon (such as 60 μm×30 μm) can be used in place of round wire. The antenna wire can be self-bonding copper wire or partially coated self-bonding copper wire, enamel copper wire or partially coated enamel wire, silver coated copper wire, un-insulated wire, aluminum wire, doped copper wire or litz wire.        The inlay substrate may be approximately 10 thousandths of an inch (300 microns) thick and may be a “synthetic paper” material such as Teslin™. The inlay substrate may have an area designated as a “transponder site” whereat the chip module will be installed. (A recess in the inlay substrate may constitute the transponder site.) The transponder site may itself have two areas designated as “terminals areas” corresponding in position to the two terminals of the chip module which will be installed at the transponder site. (The transponder site and terminal areas are generally geometric abstractions, the chip module and terminals are physical elements.) Hence, it should be understood that, where applicable, the terms (and reference numerals for) “transponder site” and “chip module” may be used interchangeably, and that the terms “terminal areas” and “terminals” may similarly be used interchangeably.        the chip module may be disposed in a recess extending into the surface of the substrate measuring for example 5.5 mm wide×8.5 mm high (generally the recess is only slightly larger than the chip module to allow some clearance during installation, while maintaining good registration)        
A conventional method to produce an inlay site on an inlay substrate containing a high frequency RFID chip (or chip module) and an antenna embedded into a multi-layer substrate and connected to the terminals (terminal areas) of the RFID chip is disclosed in U.S. Pat. No. 6,233,818 and comprises                first positioning the RFID chip in a recess, supported by a lower substrate layer (of the multi-layer substrate), then start embedding (countersinking) a wire conductor onto or into the top substrate layer in the direction of the RFID chip,        then guiding the wire conductor over a first terminal area of the RFID chip, then continuing the embedding process by forming an antenna in the top substrate layer with a given number of turns,        then guiding the wire conductor over the second terminal area, and        finally embedding the wire conductor again into the top substrate layer before cutting the wire to complete the high frequency transponder site.        
In a next stage of the production process, the wire ends passing over the terminal areas are interconnected by means of thermal compression bonding. Adhesively placing a wire conductor onto the top substrate layer is an alternative to embedding, and typically involves self-bonding coated wire conductor.
An Inlay and Transponder of the Prior Art
FIGS. 1A and 1B illustrate an inlay sheet 100 having a plurality of transponder areas (or sites). A selected one of the transponder areas 102 is shown in some detail. The vertical and horizontal dashed lines (in FIG. 1A) are intended to indicate that there may be additional transponder areas (and corresponding additional transponders) disposed to the left and right of, as well as above and below, the transponder area 102, on the inlay sheet 100. Typically, several transponders are fabricated on a single inlay sheet. In the main hereinafter the fabrication of a single transponder at a single transponder site will be discussed, except as may otherwise be noted.
The inlay sheet 100 may be a multi-layer substrate 104 comprising one or more upper (top) layers 104a and one or more lower (bottom) layers 104b. A recess 106 may be formed in (completely through) the upper layer 104a so that a chip module 108 may be disposed in the recess 106, and supported by the lower layer 104b. Alternatively, the substrate 104 may be a single layer substrate (not shown, but imaging layers 104a and 104b being a single layer rather than two distinct layers) with the recess extending only partially through the substrate.
The chip module 108 is shown having two terminals 108a and 108b on a top surface thereof. An antenna wire 110 is connected by its two end portions 110a and 110b to the corresponding two terminals 108a and 108b, respectively, of the chip module 108. In the main hereinafter the mounting and connection of only one end or end portion of an antenna wire to a corresponding one terminal of a chip module may be discussed, and may be taken as representative of how the other end or end portion of the antenna wire is connected to the other terminal of the chip module, except as may otherwise be noted.
The combination of chip module 108 and antenna wire 110 connected to the chip module at a transponder site 102 may be considered to be a transponder, and may be referred to by the same reference numeral 102. Additional layers of material (not shown) may be applied (laminated) to the transponder to make it suitable for use as a secure document such as an electronic passport or smart card. Thus, what is shown in FIGS. 1A and 1B can be considered to be an “interim product”. In the main hereinafter transponders which are interim products may be discussed except as may otherwise be noted.
The transponder 102 may be formed on an inlay substrate 104 having multiple layers comprising an upper layer 104a and a lower layer 104b, and may be exemplary of a smart card embodiment of a transponder for a secure document. A hot lamination process may be used to bond the upper and lower layers 104a and 104b together. The following dimensions are merely exemplary:                the overall thickness of the inlay substrate 104 may be approximately 450 μm        the thickness of the top layer 104a may be approximately 400 μm, and may comprise one or more layers of material        the depth of the recess 106 may be the same as thickness of the top layer(s) 104a         the thickness of the transponder chip 108 may be approximately 320 μm        the thickness of the bottom layer 104b may be approximately 240 μm, and may comprise one or more layers of material        
Generally, the recess 106 is sized and shaped to accurately position the chip module 108, having side dimensions only slightly larger than the chip module 108 to allow the chip module 108 to be located within the recess 106. And typically a dab of glue (not shown) in the bottom of the recess 106 will retain the chip module in the recess 106 during manufacturing. The following dimensions are merely exemplary:                the chip module 108 may measure approximately 5.0×8 0 mm        the recess 106 may measure approximately: 5.1×8.1 mm        the terminals 108a/b may measure approximately 5.0×1.45 mm        the wire may have a diameter between 60 and 112 μm        
One millimeter (mm) equals one thousand (1000) micrometers (μm, “micron”).
In FIGS. 1A and 1B, the recess 106 may be illustrated with an exaggerated gap between its inside edges and the outside edges of the chip module 108, for illustrative clarity. In reality, the gap may be only approximately 50 μm-100 μm (0.05 mm-0.1 mm)
In FIG. 1A the terminals 108a and 108b of the chip module 108 are shown reduced in size (narrower in width and or height), for illustrative clarity. (From the dimensions given above, it is apparent that the terminals 108a and 108b can extend substantially the full width of the chip module 108.)
It should be understood that the chip module 108 is generally snugly received within the recess 106, with dimensions suitable that the chip module 108 will not move around after being located within the recess 106, in anticipation of end portions 110a and 110b of the antenna wire 110 being bonded to the corresponding terminals 108a and 108b, respectively, of the chip module 108.
As best viewed in FIG. 1A, an antenna wire 110 is disposed, such as by embedding, on a top surface (side) of the substrate 104, and may be formed into a flat (generally planar) coil, having a number (such as four or five of “turns” (three shown), two ends, two end portions 110a and 110b, and a main intermediate portion between the two end portions. The overall length of the antenna thus formed may be approximately 1 meter.
As best viewed in FIG. 1A, the end portions 110a and 110b of the antenna wire 110 are shown extending completely over the terminals 108a and 108b of the chip module 108, from one side of the chip module 108 to the other, without (yet) being connected to the terminals 108a and 108b of the chip module 108. The end portions 110a and 110b of the antenna wire 110 may subsequently be connected, such as by thermo-compression bonding, to the terminals 108a and 108b of the transponder chip 108, respectively.
As best viewed in FIG. 1A, an intermediate portion 110c of the antenna wire 110 which is that portion of the antenna wire 110 which is between the two end portions 110a and 110b, and comprising most of the antenna wire is mounted (as indicated by the symbols “X”) in the surface of the inlay substrate 102. Only a few of the X's along the length of the intermediate portion of the antenna wire are omitted, for illustrative clarity.
As best viewed in FIG. 1A, a number of points (“a”, “b”, etc.) are illustrated along the length of the antenna wire 110 are shown. The following terminology may be used to describe different portions of the antenna wire.                the antenna wire extends between the points “a” at one “end” of the antenna wire and a point “f” at another end of the antenna wire        a short (such as 1-3 mm) portion of the antenna wire between the points “a” and “b” may be referred to as a “end segment” of the antenna wire, and generally includes the “end”. Two end segments are shown,                    one between the points “a” and “b”, and            the other between the points “e” and “f”.                        another short (6-8 mm) portion of the antenna wire which may pass over the terminal of the chip module may be referred to as the “end portion” of the antenna wire. The end portions may also be referred to as “connection portions”. Two end portions (or connection portions) are shown,                    one between the points “b” and “c”, and            the other between the points “e” and “f”.                        a main or “intermediate portion” of the antenna wire is that portion of the antenna wire which is between the two end portions, such as between the points “c” and “d”, and typically may be approximately 1 meter in length, formed with a number (such as 4 or 5) turns.        
As best viewed in FIG. 1B, the antenna wire 110 is “mounted” to the substrate 104a, which may comprise “embedding” (countersinking) the antenna wire 110 into the surface of the inlay substrate 102, or “adhesively placing” (adhesively sticking) the antenna wire 110 on the surface of the inlay substrate 102. In the main, hereinafter, mounting the antenna wire by embedding is discussed. As a general proposition, the antenna wire gets mounted (or fixed) to the inlay substrate 102 using a sonotrode tool 116 which vibrates, feeds out the wire, and embeds it into the surface of the inlay substrate 102.
Examples of embedding a wire in a substrate, in the form of a flat coil, and a tool for performing the embedding (and a discussion of bonding), may be found in U.S. Pat. No. 6,698,089 (refer, for example, to FIGS. 1, 2, 4, 5, 12 and 13 of the patent). See also FIGS. 1 and 2 of U.S. Pat. No. 6,233,818. Both of these patents are incorporated by reference herein.
It is known that a coated, self-bonding wire will stick to a synthetic (e.g., plastic) substrate because when vibrated sufficiently to soften (make sticky) the coating and the substrate.
In the case of Teslin (synthetic paper), a normal insulated wire would not properly embed into the material, it would detach. Therefore, one uses self-bonding wire which attaches to the material with a slight penetration of the wire in the material. To sink the wire into the material, it is generally necessary to pre-press the antenna with chip connected using a hot lamination press. In contrast thereto, when pre-forming a channel or groove for the wire (such as by using laser ablation or other techniques, mentioned below, see FIG. 14A, et seq.) it is not necessary to perform this pressing operation.)
FIG. 1B shows the antenna wire 110 feeding out of a capillary 116 of an ultrasonic wire guide tool (or “sonotrode”). The capillary 116 is typically disposed perpendicular to the surface of the substrate 100. The capillary 116 is omitted from the view in FIG. 1A, for illustrative clarity. In the main hereinafter the terms “capillary” and “sonotrode” may be used interchangeably, unless may otherwise be noted.
The capillary 116 may be vibrated by an ultrasonic vibration mechanism, so that it vibrates in the vertical or longitudinal (z) direction, such as for embedding the wire in the surface of the inlay substrate, or in a horizontal or transverse (y) direction, such as for adhesively placing the wire on the surface of the substrate.
In FIG. 1B, the antenna wire 110 is shown slightly spaced (in drawing terminology, “exploded” away) from the substrate, rather than having been embedded (countersunk) in the surface of the substrate, for illustrative clarity.
As described in U.S. Pat. No. 6,233,818, in a first “mounting” stage the end portions of the antenna wire are guided over the terminals of the chip module, and in a second “connecting” stage the end portions are connected to the terminals using a thermode tool to essentially weld the end portion (which may be referred to as a connection portion) of the wire to the terminal. FIG. 1B shows “generic” bond head 118, poised to move down (see arrow) onto the end portion 110b of the antenna wire 110 to bond it to the terminal 108b. 
The connecting (or interconnection) process can be inner lead bonding (diamond tool), thermo-compression bonding (thermode), ultrasonic bonding, laser bonding, soldering, ColdHeat soldering (Athalite) or conductive gluing.
As best viewed in FIG. 1A, due to the layout of the antenna coils (or turns), the antenna wire 110 may need to cross over itself. This is illustrated in the dashed-line circled area. (With a different layout of the antenna coils, such as in FIG. 4 of either U.S. Pat. Nos. 6,233,818 or 6,698,089, no such crossover is necessary.) In order to prevent shorting (electrical contact between different portions of the antenna coil) the antenna wire 110 should be an insulated wire, generally comprising a metallic core and an insulation (typically a polymer) coating. Also, the polymer coating facilitates the wire being “adhesively placed” on (stuck to) a plastic substrate layer (such as 104a).
In order to feed the wire conductor back and forth through the ultrasonic wire guide tool, a wire tension/push mechanism (not shown) can be used or by application of compressed air it is possible to regulate the forward and backward movement of the wire conductor by switching the air flow on and off which produces a condition similar to the Venturi effect. This technique may be used to create a sufficient length of residual wire for positioning adjacent a first terminal of a chip module at a transponder site. This is particularly relevant to the techniques disclosed for example in US 2010/0141453 (“brushing”).
The material for one or more layers of the inlay substrate may comprise Teslin™, a waterproof synthetic film, single-layer, uncoated with a thickness of 356 microns.    Teslin A single layer of microporous, polyolefin-based, uncoated film that bonds readily and firmly with toners, inks, adhesives and laminating films. Teslin is a waterproof synthetic material that works well with an inkjet printer, laser printer, or thermal printer. Teslin is also single-layer, uncoated film, and extremely strong. In fact, the strength of the lamination peel of a Teslin sheet is 2-4 times stronger than other coated synthetic and coated papers. Teslin comes in the sizes of 7 mil to 18 mil, though only sizes 10 mil and 14 mil are sized at 8.5″ by 11″, for printing with most consumer printers. Also available are perforated versions of Teslin, specifically, 1up, 2up, 3up, 6up, and 8up. Teslin is used widely in the production of drivers licenses, voter ID cards, and other forms of identification card. Because of its commercial availability, Teslin is also often found used for counterfeit or fake IDs. “Teslin” is a registered trademark of PPG Industries, Inc. for synthetic printing sheet.    Tyvek™ Tyvek is a brand of spunbonded olefin, a synthetic material made of high-density polyethylene fibers; the name is a registered trademark of the DuPont Company. The material is very strong; it is difficult to tear but can easily be cut with scissors or any other sharp object. Water vapor can pass through Tyvek, but not liquid water, so the material lends itself to a variety of applications: medical packaging, envelopes, car covers, air and water intrusion bathers (housewrap) under house siding, labels, wristbands, mycology, and graphics.
The material for one or more layers of the inlay substrate may comprise PVC, PC, PE, PET, PETE, TYVEK, TESLIN, Paper or Cotton/Noil. The inlay substrate can also have special markings such as luminous threads, water marks, microscopic filings and optical polymer memory for additional security.
FIG. 1C shows a transponder site similar to that of FIG. 1A, with a difference being that the ends of the antenna wire rather than end portions thereof are connected to the terminals of the chip module.
FIG. 1D shows a transponder site similar to that of FIG. 1B, with a difference being that the recess is a “pocket” type recess that extends only partially through the thickness of what is typically a single layer substrate. In contrast therewith, a recess which extends entirely through a substrate, such as the recess 106 shown in FIG. 1B extending entirely through the layer 104a, may be referred to as a “window” type recess.
Portions of the Antenna Wire
FIG. 1E shows an antenna wire, and various portions thereof, such as:                two ends which are generally the geometric “ends” of the elongate antenna wire        two end segments which are generally short portions of the antenna wire at each end of the antenna wire. The end segments include the ends, and may be connected to the terminals of the chip module, such as in US 2010/0141453 (“brushing”)        two end portions (or connection portions) which are also short portions of the antenna wire which may be connected to the terminals of the chip module, such as in U.S. Pat. No. 6,233,818 or U.S. Pat. No. 7,546,671 (“looping”)        a main or intermediate portion which is the longest portion of the antenna wire, between the two end portions, and which may be formed into several turns of a flat coil antennaSome Examples of “Final Products”        
Transponders such as are shown in FIGS. 1A,B and 1C,D may be considered to be “interim products” in that some further steps or elements may be needed before getting the product into the “hands of the consumer”. For example, various cover layers may be laminated to the inlay substrate to protect (and secure) the transponder, as well as for imprinting with information. The end result, or “final product”, may be a secure document such as an electronic passport or a smart card.
FIG. 1F shows an example of a security document which may be a National ID (identification) Card (or electronic ID, “eID” card) comprising a multi-layer (2 layer) inlay substrate, and additional layers comprising a top overlay layer and a bottom overlay layer. An RFID chip module and corresponding antenna (not shown) may be mounted in the inlay substrate(s). The chip module (not shown) may have a mold mass and a leadframe. The additional top and bottom layers may be anti-scratch layers, and protect the inlay substrate(s). The eID card, inlay substrate layer and top and bottom layers are not shown to scale.
Some dimensions for and properties of the layers may be:
Top overlay layertransparent80 micronsInlay substrate moldwhite185 microns Inlay Substrate - Leadtransparent80 micronsBottom Overlay Layertransparent80 microns
The layers of the inlay substrate for a smart card may comprise PVC, which has limited life. Smart cards are often replaced (renewed) every few years.
The layers of the inlay substrate for a national ID care may comprise PC, which may be more durable (longer life) than PCV.
FIGS. 1G and 1H illustrate an exemplary construction for an electronic passport cover, corresponding generally to the single layer inlay substrate construction shown in FIG. 1D. The inlay substrate for a US passport may comprise Teslin™.
A cover layer may be disposed over the inlay substrate 1 for the final product. The material for the cover layer may be a cloth product, with chemistry in the coatings and a leather-like appearance to the cloth, such as by Holliston Inc. (905 Holliston Mills Road, Church Hill, Tenn. 37642; www.holliston.com)
Some Examples of Chip Modules
In the main hereinafter, the discussion may focus on RFID chip modules which are leadframe-type modules. However, some of the techniques for producing security documents discussed herein may also be applicable to epoxy glass modules (chip on FR4, wire bonded, glob topped).
FIG. 1I shows an example of an RFID chip module which is a “leadframe module” comprising:                a leadframe having a thickness of approximately 80 μm        an RFID chip disposed on and connected by wire bonds to the leadframe, having a thickness of approximately 80 μm        a mold mass disposed over the chip and wire bonds, having a thickness of approximately 240 μm        an antenna wire having end portions connected to “connection areas” of the leadframe, typically on a side of the leadframe opposite the RFID chip (as shown), but the end portions can also be connected to connection areas on the same side of the lead frame as the RFID chip.        
The total thickness of the leadframe module may be 320 μm, such as for an inlay substrate having a thickness of approximately 356 μm. Generally, the chip module will be disposed in a recess in the inlay substrate so as to be concealed therein.
FIG. 1J shows an example of an RFID chip module which is an “epoxy glass module” comprising:                an interconnect substrate, such as FR4 (printed circuit board substrate material), having a thickness of approximately 100 μm (FR4 is 100 μm and the chip & glob top 160 μm=overall 260 μm)        an RFID chip, wire-bonded (alternatively flip-chip connected with solder bumps and underfiller, as illustrated) to the FR4 substrate, having a thickness of approximately 100 μm        a glob top epoxy disposed over the chip and connections, having a thickness with chip of approximately 160 μm        an antenna wire having ends connected to “connection pads”, typically on the same side of the FR4 substrate as the RFID chip, but can also be connected on the opposite side of the FR4 substrate as the chip.        
The total thickness of the epoxy glass module may be 260 μm, such as for an inlay substrate having a thickness of approximately 365 μm. Generally, the chip module will be disposed in a recess in the inlay substrate so as to be concealed therein.
Generally speaking, epoxy glass modules are inherently somewhat more flexible than leadframe modules. This is a factor that may need to be taken into consideration when incorporating an RFID module into a secure document. And, whereas leadframe modules are typically rectangular, the mold part (glob top) of an epoxy glass module are typically round.
It should be understood that, although FIG. 1J shows a flip chip connection between the RFID chip and the FR4 substrate, the chip can be wire-bonded to the substrate (such as was shown in FIG. 1I, for the leadframe-type module.)